Precise Measurement of Nitrogen Isotopic Composition Using a Quadrupole Mass Spectrometer

Abstract

A system to precisely analyze the isotope of nanogram-order nitrogen was constructed using a quadrupole mass-spectrometer. Neon and argon isotopes can also be measured by the system. The reproducibility of the nitrogen isotopic ratio is better than 3‰. The minimum amount of standard air nitrogen required for precise isotopic determination is 3 ng. The system is oriented to measure extra-terrestrial samples with low nitrogen concentration. The detail of the stepwise combustion method to separate a trace amount of indigenous nitrogen from the terrestrial nitrogen is also reported.